Light Patterns

If you’ve been making shots in a studio for a while, you’ve probably collected a number of light “modifiers” – that is, reflectors, softboxes, umberellas and other bits of metal, plastic, foil and fabric to control, block, reflect and otherwise guide the light to where you want it. But do you know what they actually do? Neil Van Niekerk tested some of his light modifiers and you can the results of Neil’s tests on his excellent blog Tangents <<- click. I thought I had better test mine. I found some interesting and one or two unexpected results.

I’m testing for 4 things here:-

The size of the light pattern

The rate of fall off at the edge, and where it starts from (ie does it fall away right from the centre, or remain fairly even up to a point, and then fall off).

The overall light intensity (how much light does each modifier eat)

The quality of shadows cast by an object in the light

All but the last few tests were conducted using a 600 Watt-second Lencarta SuperFast studio head. The light is 2.5m from the background and one stop up from minimum power to give an exposure of f/8 at ISO 100. If you’re rooting around in the EXIF, you’ll notice that it says f/4. I used a huge 50mm f/4 Zeiss lens from a Pentacon 6 medium format camera on an adapter for these tests and the camera has no idea what the aperture is actually set to. It says f/4 in the EXIF because I defined the lens in the camera’s list of manual lenses like that. On my D800/D810 bodies, these random chunks of old glass work perfectly – with full auto exposure possible, and you even get the focus indicators in the viewfinder as you move the manual focusing ring on the lens. This old (circa 1964) lens has a much larger image circle than a lens meant for a 35mm camera, and the adapter has a ball socket in it to enable tilting. I used it for this test, purely because it was to hand and most of my lenses were packed for a wedding shoot…

I also placed a C-Stand about 1m from the background to cast some shadows. I put the boom arm on it to create a T shape, as you will get different shadow quality from horizontal edges and vertical edges, if the light source is bigger in one dimension than the other. E.g. if the light source is a tall thin slit, then the vertical objects will have sharper shadows than the horizontal objects. Note: a lot of the general ripples in the light pattern, are from my saggy grey vinyl background. It’s rarely in focus in real shots, so isn’t a big issue. I am about to paint the walls Dulux Ice Storm II which is about 18% grey too – see this post by Damien Lovegrove, so I’ll be able to retire the vinyl soon.

For the last few tests, I used Speedlights (small flashguns) as they have a smaller, centrally mounted straight flash tube that does not create problems with light focusing systems like the light blaster or the Fresnel adapter. The adapter I have, like most Fresnel light focusing systems is meant for a constant LED light source which is also centrally mounted – like any theatre light that has used this technique for decades – they are not really meant for studio strobes with big round flash tubes – they may work well with hybrid lights like the Godox AD360 or AD200 that have small knots of curly flash tube.

Some observations

Grids do a good job of making a restricted beam of light. The light fall off is even, and gradual and starts near the centre of the pattern. They also retain more light overall, than say, a snoot, which absorbs a great deal of it. You also get similar size of light patterns from some wildly different sizes of modifier (standard reflector with grid vs beauty dish with grid). However, different sizes of light source also affect the shadow quality, and the smaller you get can make it (from the subject’s point of view) the sharper the shadows cast by the subject will get. You can do this by either just using a smaller light source, or moving further away so it appears smaller from the subject’s position. The snoot, for example, makes a light pattern similar to the 10 degree grid (just not as bright), but casts sharper shadows at the same distance. If I moved the grid further away the shadows will get sharper, but of course, the overall light pool will get bigger, and the light intensity will reduce as well, as the same amount of light is covering a wider area.

Barn doors are fairly useless for creating a small slit of light. This is because they are really close to the light source, and so shadows cast by the doors edges are really soft. If you want a nice controlled slit of light, cut a slit in a large piece of cardboard and hold that close to your subject while the light is further away (this is known as a cucoloris or “cookie”); or use a light focusing system like the Lightblaster, or other spot projector. Most lighting systems have a spot projector available that will take a “gobo” (GOes Before Optics). A gobo is a shape usually cut into a piece of sheet metal that is used to cast a focused sharp shadow by pumping the light through it, and then through a lens of some kind. Some spot projectors have adjustable blades in place of a fixed shape gobo, to make small slots of light.

Selfy time with the Lightblaster plus Rosco venetian blinds gobo, and reference shot with just the 7” reflector

30 degree grid. Nice smooth and gradual fall-off.

10 degree grid. Pretty much the same as the wider grid but smaller – still got that nice fall-off

Snoot. On the face of it it looks very similar to the 10 degree grid, just less bright, however the light fall off is more abrupt with a more constant, flatter, centre patch. The main difference to the grids though is the shadow quality from the C-Stand. As the snoot presents a much smaller light source, it makes much crisper shadows.

Snoot with grid – just less bright tbh.

35 degree reflector. Same amount of light, concentrated into a smaller space.

35 degree reflector with grid, gives a bright centre with the same gradual light fall-off we saw from the other grids.

Aputure small Fresnel adapter – flood. A fairly flat and wide centre circle coupled with a fairly rapid fall-off around the edges. A ring of light is visible around the edge of the circle.

Aputure small Fresnel adapter – spot. Now the ring of light around the edge is obvious – and indeed we can see that it is of course, a partially focused image of the flash tube, complete with gap where it connects to the head. This makes it fairly unusable with a flash tube, unless you can make the uneven effect work for you.

Small beauty dish. Nice ball of light with very gradual fall off and an overall wide-angle beam.

Small beauty dish with grid. You know the score by now – more gradual fall-off. The light pattern is not that different to the 7” reflector and 30 degree grid, but notice how much softer the shadow cast by the C-Stand is, due to the much bigger source.

Barn doors closed to make a horizontal slit. Pretty useless at making a slit appear on the subject, as they are too close to the light source to render an edge.

Fresnel adapter with barn doors closed to make a vertical slit. Still pretty bad.

Aputure Fresnel adapter on an SB900, spot and then flood. The straight, central flash tube make a much more appealing light pattern through the Fresnel.

YN565 in the Lightblaster with the circle gobo, in focus, and then defocused. Yongnuo 50mm f/1.8 lens used on the Lightblaster. Note how the shadow quality from the C-Stand remains the same even when the circle gobo is de-focused.

Bare YN565 speedlight – the small centrally mounted flash tubes in Speedlights make the crispest and hardest shadows, and this makes them excellent for old classic Hollywood glamour.